The manufacture of polyacrylate-containing polyvinyl chloride is well known. For this purpose, the polymerization of vinyl chloride has been conducted in the presence of the dispersion of the polyacrylic acid ester, thereby obtaining compositions of high impact resistance (cf. German Pat. No. 1,082,734; German Pat. No. 1,090,856). Utilizing this mode of operation, it has proven advantageous to perform the polymerization of the acrylic acid ester, which occurs before the graft polymerization, in the presence of small amounts of a polyunsaturated compound as the crosslinking agent (cf. German Pat. No. 1,090,857). In this way, polyacrylic vinyl chloride polymers can be produced with a polyacrylate content of up to 25% by weight (cf. German Pat. No. 1,082,734).
However, difficulties have been encountered in the polymerization and with the thus formed products if an attempt is made to produce vinyl chloride polymers which have a higher content of polyacrylic acid esters, i.e. concentrates such as are needed for the manufacture of polyvinyl chloride of high impact strength, at any desired point in time, in any desired concentration, and at any desired location.
One problem involves encrustation of deposits on the reactor wall, which increases with a rising proportion of polyacrylic acid ester. This necessitates many frequent, expensive cleaning operations involving mechanical measures or by boiling off by means of a solvent. Additionally, heat removal is interfered with, which can result in an uncontrolled progression of the reaction. The resultant products are not easily filtered and tend to stick together during drying.
These problems, which render the production of vinyl chloride polymers with high polyacrylic acid ester proportions i.e., above 25% by weight, uneconomical, are compounded by the fact that the properties of the final products are unsatisfactory for processing. The resulting particle size distribution is comparatively broad, the product becomes tacky during storage, shows poor pourability, and exhibits a low bulk density.